Hematopoietic stem cells can self-renew, differentiate to progenitor cells that give rise to the myeloid, erythroid, megakaryocytic, and lymphoid cell lineages in blood, mobilize out of the bone marrow into circulating blood, and undergo programmed cell death (apoptosis). Hematopoietic stem cells can be isolated from the blood or bone marrow.
Stem cells have commonly been characterized by their surface antigenic determinants. Such cell markers can be used to identify and isolate hematopoietic stem cells from the blood or bone marrow. The groups of cells thus isolated include some cells that are true, long-term self-renewing stem cells, some shorter-term progenitors, and some non-stem cells.
The classic source of hematopoietic stem cells is bone marrow. About 1 in every 10,000 cells in the marrow is a long-term, blood-forming stem cell; other cells present include stromal cells, stromal stem cells, blood progenitor cells, and mature and maturing white and red blood cells.
In recent years, the majority of autologous (where the donor and recipient are the same individual) and allogeneic (where the donor and recipient are different individuals) “bone marrow” transplants have actually been blood cells stem and progenitor cells drawn from peripheral circulation, not bone marrow. It is known that hematopoietic stem and progenitor cells migrate from bone marrow to blood in greater numbers by injecting the donor with for example, a cytokine, such as granulocyte-colony stimulating factor (G-CSF). The donor is typically injected with G-CSF a few days before the cell harvest. Of the cells collected, 5-20% are true hematopoietic stem cells.
There is a need for methods for mobilizing stem and/or progenitor cells from the bone marrow to the blood to facilitate harvest thereof.